I'm somewhat surprised that there hasn't been more noise around in the blogosphere about Spring 2.1's TestContext Framework. I had the pleasure of working with Juergen Hoeller for a day after JavaZone. Among other things, I learned about the fancy @Autowired annotation that you can use to make your autowiring much safer. Normally autowiring is considered bad practice, but it was Juergen's advice that now it is okay to use. This means in practice that all your service beans will still be declared in an applicationContext.xml file, but the dependencies and object graphs will be annotated in the Java files (or atleast where you see fit).
After this I had a deeper look into the features of Spring 2.1. Note the point about "our next-generation Spring TestContext Framework with support for JUnit4". Now this is cool.
Why we need it (or something like it)
For a long while I (and many of my colleagues and peers) have been annoyed by the disability to manage tests as the amount grows. There hasn't been any good framework around for doing any kind of categorization of tests. Each project would have to invent their own set of hacks in order to control their test suites, be it a TestFactory picking up system variables, or using different Maven profiles and source folders for different categories of tests. In short, inventing some sort of convention for seperating tests: put them in different folders, use name conventions like *Test.java, and *IntegrationTest.java.
Have you ever been in a project where you and your team dropped automated testing because you couldn't manage the mass of tests? Well, tools are starting to appear now that can save your hiney.
TestNG solves this. Why don't you just use that?
The first solution that many have become aware of is TestNG. I really like the feauteres, but as of Alex presentation on JavaZone, Maven's surefire plugin still has issues running TestNG. Also, Eclipse (our standard IDE) has built in support for JUnit4. And finally, Spring comes with a bunch of lovely standard testbase classes that make your integration tests nicer. Oh, wait. You don't want your test to inherit from a Spring class? Read on to find out. Final reason: everyone knows JUnit and not too many know TestNG (sorry Alex..).
There's a new kid in town
Spring TestContext Framework introduces a wide range of new annotations for doing tests, my absolute favourite being the @IfProfileValue that you can use to specify testing environment (in other words implement the test categorization I spoke of above). There is only one implemented ProfileValueSource (being the logic that decides which profile it is) that checks for system variables, but it is easy to extend with your own ProfileValueSource class that contains the logic for deciding which tests to run.
As promised: avoid extending Spring's testbase classes: Use the @RunWith(SpringJUnit4ClassRunner.class annotation instead.
You got the regular nifty annotations like @Repeat (guess what it does) @Timed (fails if the tests exceeds a time limit, different from JUnit 4's timeout attribute), plus a bunch of Spring environment controlling transactions and Spring contexts. You don't need to use the @ExpectedException any more because JUnit4 supplied us with the @Test(expected=RuntimeException.class) functionality. Spring people recommend that you use JUnit's way of doing it.
"Caching between testing", and "injection of test fixtures". Sounds lovely, doesn't it? Sounds alot like the presentation of TestNG, but hey, it's JUnit :)
There is also a pretty cool @ContextConfiguration annotation for declaring which Spring bean XML files you want to use for a particular test.
Actually, instead of me repeating the whole documentation, why don't you take a look for yourself. Note that I haven't actually played around with this properly yet (well, we got as far as getting the M4 build into our maven repository) cause I left my laptop in work. I'm gonna try setting up the machine here tonight and see if I can get something done before bedtime.
By the way, some shameless company promotion: My employer is doing a course on Spring 2 with Interface21 in Oslo in the beginning of November. Per is a really friendly guy, so don't hesitate to give him a call and ask about it if you're curious :)